In the field of ophthalmology, the commercial sale of eyeglasses has presented several problems. First of all, the oculist usually carries glasses frames that are both manufactured in foreign countries, as well as in the United States. The metric system of threads is usually used in foreign products, while the United States has its own standard, the two thread systems being different. The problem arises, particularly, in the case of the bolt which hinges the bows of the eyeglass to the main frame. It is not readily evident as to which type of thread is used in connection with the particular pair of glasses so that, even though the oculist may store bolts of the two types, he usually has difficulty deciding which one to use. The problem is particularly acute in repairing eyeglasses, since damage often takes place in the hinge itself. The customer who repairs his own eyeglasses usually must buy two bolts in order to be sure that when he arrives home, he has a bolt with the proper type of thread. Even so, he may damage the threads (on the bolt or in the hinge), while experimenting to determine which bolt will fit the thread in his hinge.
Some improvements have been made in the past in the so-called "temple" hinges. For instance, the U.S. patent of Weisgerber, U.S. Pat. No. 4,145,124, shows a bolt for use in an eyeglass hinge, which bolt has a tapered, serrated shank to lock it in place. The U.S. patent of Okner, U.S. Pat. No. 3,029,697, shows an eyeglass construction in which the resilience in a slit hinge ear is used to prevent the hinge bolt from loosening.
Considerable attention has also been paid to problems encountered in the field of machine threads, such as that shown in the U.S. patent of Bates, U.S. Pat. No. 1,447,056; in that patent a non-standard thread is used on a nut to lock it in place on the bolt. Similarly, the U.S. patent of Darling, U.S. Pat. No. 4,013,110, shows the use of threads of slightly different leads to promote locking. The U.S. patent of Miller, et al, U.S. Pat. No. 4,033,615, describes a system by which a valve port can accept any one of several standard pipe threads by providing the port with threads having a pitch midway between the NPT and the BSP pitches and using both tapered and parallel threads. The British patent No. 929,565 describes an electrical element consisting of a screw-threaded pin that is provided with both metric and English-measure threads. The British patent No. 1,454,769 describes a locking thread fastener having a root which is varied along its length to promote interference. All of these constructions require expensive thread-forming procedures and do not lend themselves to use with eyeglasses. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.
It is, therefore, an outstanding object of the invention to provide an eyeglass hinge system that permits the hinge to be easily repaired, irrespective of whether the eyeglasses were manufactured in the U.S. or in foreign countries.
Another object of this invention is the provision of a hinge construction for use in eyeglasses, which construction includes a bolt that is acceptable to both metric and U.S. standard threaded bores.
A further object of the present invention is the provision of a bolt that can be used by oculists or eyeglass owners to easily repair an eyeglass hinge.
A still further object of the invention is the provision of a system whereby foreign and domestic eyeglass manufacturers can use their own country's thread standard without acceptance problems in other countries.
It is a further object of the invention to provide an eyeglass hinge construction that permits repair of damaged eyeglasses without the necessity of determining which thread standard is used in the hinge.
With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.